System and method for managing emergency requests

ABSTRACT

A network component is provided. The network component including a component configured such that the network transmits a response message containing an indicator indicating that a first message is an emergency-related request, and such that the network receives a second message containing information associated with a user equipment (UE).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/253,036 filed on Aug. 31, 2016, which is a is a continuation of U.S.patent application Ser. No. 14/968,686 filed on Dec. 14, 2015, which isa continuation of U.S. patent application Ser. No. 12/937,199 filed onJan. 13, 2011, which is a filing under 35 U.S.C. 371 of InternationalApplication No. PCT/US2009/045990 filed Jun. 2, 2009, entitled “Systemand Method for Managing Emergency Requests” claiming priority to U.S.patent application Ser. No. 12/131,785 filed on Jun. 2, 2008, andclaiming priority to U.S. Provisional Application No. 61/061,507 filedon Jun. 13, 2008, and claiming priority to U.S. Provisional ApplicationNo. 61/081,576 filed on Jul. 17, 2008 which these applications areincorporated by reference herein in their entirety.

BACKGROUND

The IP (Internet Protocol) Multimedia Subsystem (IMS) is a standardizedarchitecture for providing multimedia services and voice-over-IP callsto both mobile and fixed user equipment (UE). The Session InitiationProtocol (SIP) been standardized and governed primarily by the InternetEngineering Task Force (IETF) as a protocol for setting up and managingIMS-based calls. As used herein, the term “UE” can refer to mobiledevices such as mobile telephones, personal digital assistants, handheldor laptop computers, and similar devices that have telecommunicationscapabilities. Such a UE might consist of a wireless device and itsassociated Universal Integrated Circuit Card (UICC) that includes aSubscriber Identity Module (SIM) application, a Universal SubscriberIdentity Module (USIM) application, or a Removable User Identity Module(R-UIM) application or might consist of the device itself without such acard. The term “UE” may also refer to devices that have similarcapabilities but that are not transportable, such as fixed linetelephones, desktop computers, or set-top boxes. The term “UE” can alsorefer to any hardware or software component that can terminate a SIPsession.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of this disclosure, reference is nowmade to the following brief description, taken in connection with theaccompanying drawings and detailed description, wherein like referencenumerals represent like parts.

FIG. 1 is a diagram of an illustrative IP network including a UE and aPSAP according to an embodiment of the disclosure.

FIG. 2 is a diagram of an illustrative IP network including a UE and aPSAP according to another embodiment of the disclosure.

FIG. 3 is a diagram illustrating a method for a UE to respond to anemergency-related message according to an embodiment of the disclosure.

FIG. 4 is a diagram of a wireless communications system including userequipment operable for some of the various embodiments of thedisclosure.

FIG. 5 is a block diagram of user equipment operable for some of thevarious embodiments of the disclosure.

FIG. 6 is a diagram of a software environment that may be implemented onuser equipment operable for some of the various embodiments of thedisclosure.

FIG. 7 is an illustrative computing system suitable for some of thevarious embodiments of the disclosure.

DETAILED DESCRIPTION

It should be understood at the outset that although illustrativeimplementations of one or more embodiments of the present disclosure areprovided below, the disclosed systems and/or methods may be implementedusing any number of techniques, whether currently known or in existence.The disclosure should in no way be limited to the illustrativeimplementations, drawings, and techniques illustrated below, includingthe exemplary designs and implementations illustrated and describedherein, but may be modified within the scope of the appended claimsalong with their full scope of equivalents.

In an embodiment, a user equipment is provided. The user equipmentincluding a component, such that responsive to making an emergencyrequest that is rejected, the component configured to receive a messagecontaining information associating the emergency request with a combinedemergency centre.

In another embodiment, a network component is provided that includes acomponent, such that upon receiving an emergency request from a userequipment, the component configured to determine whether the emergencyrequest is related to a combined emergency centre and to send the userequipment a message containing information identifying that theemergency request is related to a combined emergency centre.

A user of a UE, such as an IMS-capable UE, can typically place anemergency call by dialing 911 (in North America), 112 (in most ofEurope), 999 (in the United Kingdom), 110, 118, or 119 (in Japan), orsome other emergency-specific number. Such a call may be handled by aPublic Safety Answering Point (PSAP), which might be an emergency callcenter or system that can coordinate an appropriate response to theemergency. Any call made to a PSAP will be referred to herein as anemergency call. In this document, a PSAP could also be an emergencycentre or emergency centers.

In some cases, a UE might not be aware that a call that it placed was anemergency call. For example, a UE manufactured for use in North Americamight be programmed to recognize that a call to 911 is an emergencycall. If such a UE is taken to a country where a number other than 911is used for emergency calls, and the UE user dials that other emergencynumber, the UE might not recognize the call as an emergency call.Undesirable results may occur if the UE does not recognize that a callis an emergency call. For example, the UE could fail to provide relevantinformation to the PSAP, the UE may treat the call as a regular call andplace it on hold or call waiting, the call could be blocked, or the UEmight otherwise fail to treat the call appropriately. In addition, thenetwork may not apply special treatment, for example, in a congestednetwork or cell, and the unrecognized emergency call may not besubjected to emergency call procedures (e.g., may not receive priority).

The present disclosure provides for indicating to a UE that a call thatthe UE placed was an IMS emergency call by including in a message to theUE an indicator that the call was an emergency call. The indicator mightbe included in a SIP message that may be but is not limited to a SIP 2xxor SIP 1xx message sent to the UE in response to an initial SIP requestfor a dialog or standalone transaction, or unknown method (e.g., a SIPINVITE request), or a similar message, that the UE sends in attemptingto set up the emergency call. Hereinafter, the term “SIP message” mayrefer to a SIP request (including, e.g., a re-INVITE request or a Targetrefresh request for a dialog or an initial SIP request for a dialog orstandalone transaction, or an unknown method) or a SIP response. Itshould be noted that the re-INVITE method request can only be sent whenconditions documented in the Internet Engineering Task Force (IETF)Request for Comments (RFC) 3261 are satisfied. The SIP message thatincludes the indicator might be sent by the PSAP or by a component of anetwork through which the PSAP and the UE communicate with one another.Examples of such components are P-CSCF and E-CSCF.

The emergency-related indicator can be encoded in SIP using thefollowing alternatives: a) SIP bodies such as “application/3gpp-ims+xml”have been used in IMS to indicate additional information or directivesto receiving UAs. It can be extended to also indicate to the UE that,upon receipt in an INVITE or similar request, the request is to be takenas an emergency call or PSAP callback and that the functionalityassociated with calls of such type is to be invoked. This functionalitymay include but it not limited to alerting the user by visual, audible,or other methods as well as including location information in theresponse. A new content-disposition header field value may need to bedefined. b) A new SIP header could be defined or an existing SIP headercould be enhanced. The PSAP itself or the S-CSCF handling the PSAP callback on behalf of the PSAP or another network element such as asignaling gateway can introduce an indicator. c) The indicator could bea new SIP header field. d) The indicator could be a new SIP header fieldvalue, e.g., a standardized SIP URN indicating the PSAP function (e.g.mountain rescue or coast guard or general 911) or emergency centrefunction or emergency personnel function. e) The indicator could be anew URI field. f) The indicator could be a new URI field value, e.g.,user=psap, where ‘user’ is a SIP URI field and ‘psap’ is a new valuethat might be put in the Contact header field. g) The standardized SIPURN could be put in the P-Asserted-Identity by the trust domain in whichthe PSAP or emergency centre or emergency personnel resides. h) Theindicator could be contained in the FROM header field value and the FROMheader field value can be asserted according to RFC 4474 or RFC 3893.This solution is based on certificates.

As identified above, a number of possibilities could be used to indicatethat a session is in fact an emergency session. It has been highlightedthat the PSAP could be in a visited network such as a VPLMN network andhas no trust relationship with the home network such as an HPLMN (HomePublic Land Mobile Network). Assuming this is the case when the UE issetting up an emergency session the UE doesn't recognize or whenreceiving a mobile terminated request containing an indication in theSIP message (e.g., 1xx or 2xx responses or a SIP target refresh requestor a similar message) that the request is a PSAP callback, the PSAP orthe network could also send back a token that the UE would store. Thenetwork could provide this token when the UE registers with IM corenetwork (CN) subsystem. The token could be stored in memory, which couldbe internal or removable. In the event the UE's emergency call isdisconnected or the UE needs to be informed it is requesting anemergency session, the network or PSAP could include this token. Uponreceipt of the token from the network, the UE can compare it to theshared token. If the tokens do not match, the UE knows the call is notemergency related.

The SIP “priority” header field set to “emergency” has so far not beenused as a trusted indicator for emergency call [RFC 3261]. The installedbase of SIP UAs will have different and diverging treatment for thisheader, if any treatment.

In the event the PSAP callback or emergency call signaling response isreceived over a Circuit Switched network, the solution can allow formapping between appropriate Calling-Party-Category fields which issometimes used to carry the indication of an emergency call in ISUP/TUP(ISDN User Part/Telephone User Part) based systems. Typically, theISUP/TUP signaling information does not allow for a granularity as fineas the emergency urn:service:sos identifiers defined in RFC 5031.

FIG. 1 illustrates a system 10 that includes one or more componentsassociated with an IMS network 120. A UE 110 may be any end user deviceor system that can connect to the IMS network 120. Examples of the UE110 can include, but are not limited to, mobile phones, fixed linephones, mobile wireless devices (including digital, cellular, or dualmode devices), personal digital assistants, laptop/tablet/notebookcomputers, and desktop computers. The UE 110 can communicate via the IMSnetwork 120 with a PSAP 130, which may be a 911 system or anotheremergency call center or system.

The IMS network 120 might include any well known set of components, suchas base stations and other radio transmission and reception equipment,that can promote an IMS-based connection between the UE 110 and the PSAP130. Other components that might be present in the IMS network 120 butthat are not shown include a P-CSCF (Proxy Call Session ControlFunction) that may be the first point of contact for the UE 110; anS-CSCF (Serving CSCF) that may perform session control, downloading anduploading of user profiles, and other functions; an E-CSCF (EmergencyCSCF) that may provide session control functions for the PSAP 130; andother well known components for initiating and maintaining IMS-basedsessions.

To make an emergency call, the UE 110 might send an initial SIP requestfor a dialog or standalone transaction, or unknown method (e.g. a SIPINVITE request) 140, or a similar invitation message, to the PSAP 130via the IMS network 120. The PSAP 130 typically responds to theinvitation message 140 with a SIP 1xx or SIP 2xx response (e.g., SIP 200OK) message 150, or a similar response message. Alternatively, the PSAP130 could transmit a target refresh request (e.g. re-INVITE request).Standard SIP procedures might then be followed to establish theemergency call between the UE 110 and the PSAP 130.

In an embodiment, the response message 150 includes an indicator 160that indicates that the call placed by the UE 110 was an emergency call.The indicator 160 may be a bit, a flag, or some other data element thatis recognizable by the UE as a designation that a call placed by the UE110 was an emergency call (e.g., emergency service URNs as specified inRFC 5031 such as urn:service:sos, urn:service:sos.animal-control, orurn:service:sos.police, if it is determined that the call that wasplaced can be categorized as, e.g., a urn:service:sos call, aurn:service:sos.animal-control call, or a urn:service:sos.police call).When the UE 110 receives the response message 150 that includes theindicator 160, the UE 110 identifies that the call it placed was an IMSemergency call and can then take appropriate actions and invokefunctionality for an emergency call. One action that the UE 110 mighttake is to indicate to the UE user the nature of the original call. Thatis, the UE 110 might alert the user that the call was an emergency call.The alert might be a message that appears on the display screen of theUE 110, a visual or audible alert, or some other type of environmentalcondition or indication of the nature of the call. Other actions takenby the UE 110 can involve transmitting a SIP request message 170 such asa SIP ACK or SIP PRACK message or any subsequent SIP request part of thedialog (including target refresh requests) or request for a new dialog,where the request for the dialog uses the SIP Target-Dialog header fieldwith a value set identical to the corresponding dialog identifier valuefor the emergency session. In the case of sending a request for a newdialog message 170 with SIP Target-Dialog header field set, it canindicate to the recipient that the sender is aware of an existing dialogwith the recipient, either because the sender is on the other side ofthat dialog, or because it has access to the dialog identifiers, therecipient can then authorize the request based on this awareness.Subject to limitations of SIP, either of these messages can includeinformation in the request as part of information available to the PSAP130 if the recipient is the PSAP 130. As mentioned, the message 170might be a SIP target refresh request, a SIP UPDATE, a SIP re-INVITEmessage 170, or a similar (acknowledgement) message (e.g. SIP PRACK).The message 170 can include information 180 about the UE 110, to bedescribed in detail below. Due to limitations in the SIP protocol, theinformation 180 may be spread over several SIP messages, e.g. someinformation may be in SIP PRACK requests, some in responses to PSAP- ornetwork-originated requests or SIP UPDATE requests, and some in otherSIP target refresh requests. The information 180 might be intended forthe PSAP 130 or for one or more components in the IMS network 120. Theinformation 180 could optionally include a flag or other indicator thatindicates that certain emergency-related information, such asidentification, network access, and location information, is not to beshared (e.g., with the PSAP 130). If one or more privacy indicators areset, the network might still be able to use the emergency-relatedinformation for routing purposes or to provide anonymous call-back.

In another embodiment, a policy could be stored in the UE 110. Thepolicy or policies can be used to determine if including one or moreindicators to request privacy when requesting emergency sessions isallowed, or if emergency-related information is provided when a PSAPmakes a call-back, or if it is allowed to request privacy whenemergency-related information is provided in response to a PSAPcall-back. The policy could be consulted when the UE 110 wants todivulge information that is sensitive to privacy, such as, but notlimited to, location. The policy could be user-provided,operator-provided, or both. When the information is both user-providedand operator-provided, the operator might provide a default policy, butthe user might be able to override this policy if they so wish. Thepolicy can be stored in memory that is either internal or external tothe device.

It is possible that the policy/preference could be set up in a way thatis against the PSAP's regulatory requirements. For example, the UE 110might come from a country where it can choose whether or not to provideuser-related or event-related information, and the policy/preference maybe set such that the information will not be provided. Alternatively,the policy/preference may be set such that the information may beprovided (e.g., for the purposes of determining the nearest PSAP), but arequest might be made that the information not be released. The UE 110may subsequently go to a country where by law location information mustbe provided if available. In such cases, the network might signal to theUE 110 that the policy/preference is overridden and that informationmust be provided. This override notification could be signaled as atoken in a message from the network. For example, a SIP message couldcontain a token that is coded as a new feature tag, a new URI parameter,an XML body, an SDP parameter, or a similar coding feature. The tokenmight also need the property that it can be trusted by the UE 110.

The following illustrates one possible embodiment of how the UE 110 maybehave.

Basic procedure will be Policy / Preference set Message received fromnetwork containing override token Consult preference / policy Allowlocation information provide Not allowed determine if token receivedToken received ascertain authenticity of token and if valid providelocation information Token received, fake, provide indication to networkfake token received, provide no location information.

The token could be carried in a callback from the PSAP 130, such as aSIP INVITE. Alternatively, the token could be provided at the time theUE 110 makes registration with the network 120, such that in IMS thetoken could be provided in a SIP 200OK message in response to anemergency registration. Within the 200OK, if the token is coded as a newfeature tag, a new URI parameter, or an XML body, the token might be asecure token. In an LTE/SAE network, the 200OK message could betransmitted in response to a request to attach to the network or as partof the authentication sequence of the UE 110.

Another embodiment is that the VPLMN policy could be broadcast in asystem message indicating the behavior of the UE should it receive anemergency callback.

The provisioning of the policy can be performed in, but is not limitedto, one of the following ways: OMA DM, CP, OTA, proprietary, or other.When being provisioned, any of the following transports could be used:Cell Broadcast, SMS, USSD, MBMS, Generic IP pipe, or other.

The policy might be stored in internal or external memory. Externalmemory might be, but is not limited to, PC Card PCMCIA, CompactFlash ICF-I, CompactFlash II CF-II, SmartMedia SM/SMC, Memory Stick MS, MemoryStick Duo MSD, Memory Stick PRO Duo MSPD, Memory Stick PRO-HG Duo MSPDX,Memory Stick Micro M2, Multimedia Card MMC, Multimedia Card RS-MMC,MMCmicro Card MMCmicro, Secure Digital Card SD, SxS SxS, Universal FlashStorage UFS, miniSD Card miniSD, microSD Card microSD, xD-Picture CardxD, Intelligent Stick iStick, Serial Flash Module SFM, μ card μcard, NTCard NT NT+, USIM, R-UIM, etc.

In one embodiment of the policy information, there would be a file onthe removable memory consisting of eight bits for each file. Bit 1 (theLeast Significant Bit) might be set to 1 to indicate that locationinformation is to be provided, or to 0 to indicate that locationinformation is not to be provided. All remaining seven bits could bereserved (RFU). The user preference file could be under PIN control(i.e., the user could, after entering the PIN, control the content ofthe file), and the operator file could be under ADM (Administrative)control, preventing any party, other than the administrator (the cardissuer, usually the carrier) from altering the contents of the file.

In various embodiments, the policy may be implemented in differentformats. One example of a format for the policy is provided below, butthe formats should not be limited by this example, as other formats arecontemplated.

/<X>/Emergency Location policy upon PSAP call back/ The EmergencyLocation policy leaf indicates whether the UE provides emergencyinformation or not for emergency call back. • Occurrence: One • Format:bool • Access Types: Get, Replace • Values: 0, 1 0 - UE providesemergency information. 1 - UE does not provide emergency information.<Node> <NodeName> Emergency Location policy </NodeName> <DFProperties><AccessType> <Get/> <Replace/> </AccessType> <DFFormat> <bool/></DFFormat> <Occurrence> <One/> </Occurrence> <DFTitle> EmergencyLocation policy </DFTitle> <DFType> <MIME>text/plain</MIME> </DFType></DFProperties> </Node

As mentioned previously, when the UE 110 receives the response message150 that includes the indicator 160, the UE 110 might transmitinformation 180 about itself to the PSAP 130. If policy allows, onepiece of the information 180 that the UE 110 might include in the SIPmessage 170 is the UE's public user identities (such as Tel URI, SIPURI, or Mobile Station International ISDN Number (MSISDN)) or some otheridentifying symbol. Including such information could be subject topolicy or could be accompanied by an indicator that private informationis not shared with the PSAP or emergency centre or untrusted networkelements. The public user identities might be in GRUU format or maycontain sufficient information that a callback over Circuit Switchtechnology is possible, e.g., in Tel URI format. The PSAP 130 can usethe identifier to make a callback to the UE 110 if necessary, asdescribed below. Another piece of information 180 that the UE 110 mighttransmit in the acknowledgement message 170 is the type of access thatthe UE 110 is using. For example, if the emergency call is being madeover a wireless local area network (LAN), the UE 110 might include thatfact in the information 180, as well as a cell ID, a line ID, and/or awireless LAN access node ID. During the dialog, the points of attachmentto the IP-Connectivity Access Network (IP-CAN) of the UE can change(e.g., UE connects to different cells). The UE can populate theP-Access-Network-Info header in any request or response within a dialogfor which transmission of such information is supported (e.g., excludingACK requests and CANCEL requests and responses), with the current pointof attachment to the IP-CAN (e.g., the current cell information).

If the UE 110 is aware of its geographic location, e.g., through the useof a global positioning system (GPS), the UE 110 can include itslocation as another piece of the information 180, such as but notlimited to Cell Global Identity (CGI), Service Set Identifier (SSID),waypoints such as landmarks, and the signal strength of adjacent cellswith corresponding CGIs. If the UE 110 is not aware of its geographiclocation, location-related data is not included in the information 180.If a GRUU (globally routable UA (user agent) URI (uniform resourceidentifier)) is associated with the UE 110, the UE's GRUU can beincluded as another piece of the information 180. Depending on theprivacy settings of the user, the GRUU may be a P-GRUU or a T-GRUU,although a public GRUU (P-GRUU) is preferred over a temporary GRUU(T-GRUU).

Other items that can be included in the information 180 might includethe capabilities of the UE 100, the radio access technology being usedby the UE 110, the battery life of the UE 110, the signal strength, andthe network identity (e.g., CGI, SSID, SID). The UE 110 could alsoinvoke what is commonly known as ecall functionality to be sent to thePSAP 130.

Before the emergency request reaches the PSAP 130, it might be handledby one or more components in the IMS network 120. Examples of suchcomponents are the P-CSCF, E-CSCF, AS, and IBCF (Interconnect BorderControl Function). An IMS network component, such as P-CSCF, AS, andE-CSCF, can inspect all requests in order to determine if they arerelated to emergencies. If a request is determined to relate to anemergency, based on configurations and regulator policies, the networkcomponent can determine to reject the request or update the request orinclude the emergency call indicator 160 in a SIP response that is sentto the UE 110. Updating the request might be done if the UE provides aT-GRUU and the network operator policy settings (e.g., in the P-CSCF)indicate that the public user identities must be provided. In such acase, the T-GRUU can be replaced with the GRUU. In addition, updating ofmessages to be routed to PSAPs might be done if the message containsP-Preferred-Service header fields, P-Asserted-Service header fields,Accept-Contact header fields containing one or more IMS CommunicationService Identifier (ICSI) values (coded as specified in subclause7.2A.8.2 in 3GPP TS 24.229) or one or more IMS Application ReferenceIdentifier (IARI) values (coded as specified in subclause 7.2A.9.2 in3GPP TS 24.229) that are related to the request in a g.3gpp.app_reffeature tag. Note that the network element can be in Back to Back UserAgent (B2BUA) or proxy role when updating these SIP requests orresponses. Note that if the network element is an AS, there is a needfor a new reference point between the AS and at least one of IBCF,E-CSCF or P-CSCF as at the moment there is only a service controlreference point between AS and S-SCSF or I-CSF. The P-Preferred-Serviceheader fields, P-Asserted-Service header fields should not be forwardedto the PSAP or emergency centre. The Accept-Contact header fields shouldbe groomed for ICSI values and IARI values as they may causeinteractions when selecting a SIP user agent terminating the session atthe PSAP. If the Accept-Contact header field contains g.3gpp.app_refmedia feature tags, they and their values shall be removed. If theAccept-Contact header field contains g.3gpp.app_ref media feature IARIItags, they and their values can be removed.

In other words, what is termed “updating” can include changing the GRUUfrom a temporary GRUU into a public GRUU. This is done because atemporary GRUU is invalid if the UE is disconnected and has toreregister. A PSAP cannot make a callback to a temporary GRUU after theUE de-registers and re-registers. Public GRUUs, on the other hand, havethe property that they are routable even after the UE de-registers andre-registers (making a PSAP callback to that public GRUU more likely tocomplete). “Updating” can also include not propagating of ICSI or IARIfeature tags, P-Preferred-Service header fields, and/orP-Asserted-Service header fields. The presence of such tags or fieldsmight skew the handling of the request at the PSAP and cause the requestto be routed based on services supported on the UE rather than, forexample, on geographical proximity and type of service requested. Sincethere is typically not an S-SCSF and not a (MultiMedia Telephony)Application Server in the session path between the UE, the P-CSCF, theE-CSCF, and the PSAP, these services the UE supports are typically notavailable during the emergency call. So signaling it as part of anemergency request (even when the UE did not realize it is an emergencyrequest and includes ICSI or IARI feature tags, P-Preferred-Serviceheader fields, and/or P-Asserted-Service header fields because itbelieves the request it makes is a normal request) does not serve anypurpose and may only detract/result in routing the requests to otherPSAPs or PSAP User Agents than those determined based on location,requested type of service, and RFC 3261 procedures. In a worst casescenario, if a PSAP User Agent registers its support for said services,it may receive a higher load of emergency service requests than otherPSAP User Agents, possibly leading to delay in the emergency response.

In the embodiments where a component in the IMS network 120 rejects theemergency service request, it can respond with a SIP 3xx message, suchas a 300 (Multiple Choices), 301 (Moved Permanently), 302 (MovedTemporarily), 380 (Alternative Service) message, or a SIP 4xx responseor a SIP 6xx response. A SIP 380 (Alternative Service) is preferablyused to indicate that the UE should try another access technology suchas CS, or use/create another secure context/registration such as thecontext created by the emergency registration. The message can also beused to inform the UE to not use the present context (which might havebeen created as a result of an emergency registration).

The following are cases where the network may be configured to rejectthe request: a) the network is not able to handle emergency sessions; b)the IM CN subsystem to which the P-CSCF belongs is not able to handleemergency sessions; c) due to local policy, the network does not handleemergency sessions; d) the network only handles certain types ofemergency session requests; e) the UE is roaming; f) the P-CSCF is in adifferent network than the UE's home operator's network; g) the networkdoes not support emergency sessions for either the geographical locationwhere the UE is located or the IP-CAN to which the UE is attached.

It should be noted that a 3xx redirection response may be valid orroutable in the currently attached network only. For example,urn:service:sos.animal-control may be valid in the address book only forsome networks to which the UE 110 can attach/register. Usage of anaddress in the address book can be conditional to the operator or regionto which the UE 110 is attach/registered. A 3xx response urging the UEto use another address for this emergency-related request or a requestdetermined to be not related to an emergency should not be followed bysimply changing the corresponding address book entry, if present, in theaddress book.

Two examples can illustrate cases where the network rejects the requestbecause the type of emergency session request is not supported. In thefirst example, RFC 5031 defines urn:service:sos.aninmal-control asfollows: Animal control typically enforces laws and ordinancespertaining to animal control and management, investigates cases ofanimal abuse, educates the community in responsible pet ownership andwildlife care, and provides for the housing and care of homelessanimals, among other animal-related services. In some jurisdictions, arequest to urn:service:sos.aninmal-control may not be classified as anemergency in the sense that it is subjected to network and operatoremergency procedures (e.g. allow or disallow a request tourn:service:sos.aninmal-control when the UE didn't register or hasinsufficient credentials). If so configured, the network could eitherreject with an indication that the call is not actually an emergency orit could reject with an indication that the call is not an emergency andoffer alternative steps to be executed such as offering a different URIto contact and/or a different Circuit Switched (CS) network address suchas a digit string. Note that, since emergency service URNs are notroutable and are not E.164 numbers, the UE may not be able to proceedlacking knowledge of routable addresses or numbers. In thosejurisdictions, it would be inappropriate if the UE executed emergencyprocedures (as specified in 3GPP TS 24.008) and a UE should notautomatically contact, for example, “911” or “112” “upon receiving arejection when contacting, e.g., urn:service:sos.aninmal-control.

Note that it is possible that a CS-enabled UE has received a list oflocal CS emergency numbers (e.g. received a result of theLocation-Update procedure). A UE could indicate the requested emergencyservice type in a CS emergency request and be connected to the requestedPSAP using procedures in 3GPP TS 24.008. E.g., the following tableexists:

Table 10.5.135d/3GPP TS 24.008: Service Category information elementEmergency Service Category Value (octet 3) The meaning of the EmergencyCategory Value is derived from the following settings (Please see 3GPPTS 22.101 clause 8): Bit 1 Police Bit 2 Ambulance Bit 3 Fire Brigade Bit4 Marine Guard Bit 5 Mountain Rescue Bits 6,7,8 are spare and set to “0”Mobile station may set one or more bits to “1” If more than one bit isset to “1”, routing to a combined Emergency centre (e.g. ambulance andfire brigade in Japan) is required. If the MSC can not match thereceived service category to any of the emergency centres, it shallroute the call to an operator defined default emergency centre. If nobit is set to “1”, the MSC shall route the Emergency call to an operatordefined default emergency centre

However, at present no mapping for urn:service:sos.animal-controlexists. A mapping for some other emergency services as defined in RFC5031 (e.g. urn:service:sos.police) can be made by setting thecorresponding bit in Emergency Category Value (e.g.urn:service:sos.police maps to Bit 1 of the Emergency Service CategoryValue, urn:service:sos.ambulance maps to Bit 2 of the Emergency ServiceCategory Value, urn:service:sos.fire maps to Bit 3 of the EmergencyService Category Value, urn:service:sos.marine maps to Bit 4 of theEmergency Service Category Value, urn:service:sos.mountian maps to Bit 5of the Emergency Service Category Value).urn:service:sos.animal-control, urn:service:sos.physician,urn:service:sos.poison, urn:service:sos.gas, and others could map to anEmergency Service Category Value with no bits set “1”, causing the callto be routed to an operator-defined default emergency centre.Alternatively, for requests for which no PSAP is supported in thenetwork, the UE could be instructed to make a normal SIP request (usingprocedures in 3GPP TS 24.228) or setup a normal CS call (usingprocedures in 3GPP TS 24.008). The network could accomplish such by notindicating an alternative address that cannot be mapped to an EmergencyService Category Value (i.e. not one of the urn:service:sos URNs forwhich a mapping is standardized). When an emergency request is receivedby the PSAP but the PSAP cannot handle the request and returns a SIP 380or a similar message, if a mapping exists on the UE from the given URNto an Emergency Service Category Value, a call shall be setup to that CSPSAP E.164 number automatically.

In the second example: the P-CSCF may determine that the emergencyrequest is made to urn:service:sos.police. However, for example in theNetherlands, contacting the police does not per definition warrantactivating emergency procedures. Instead, a special number differentfrom “112” is configured: 0900-8844. Other examples are “19” Police(Albania)”, “100” (Police and Fire Brigade (Greek cities)), “100”(Ambulance and Fire Brigade (Belgium)), “112” (Police and Ambulance(Italy)), “112” (General emergency call, all categories (Sweden)), “115”(Fire Brigade (Italy)), “144” (Ambulance (Austria)), “*377” (localpolice agency or Department of Public Safely office, non-emergencyroadside assistance in Texas). Such a number may be a premium service.It could be inappropriate if the UE automatically contacted, forexample, “911” or “112” if the network rejects the call tourn:service:sos.police, and it could be inappropriate if the networkautomatically contacted, for example, 0900-8844 as a regular call as theuser, without realizing it, may then automatically receive premiumcharges. The P-CSCF could provide alternative steps such as providing adigit string, e.g., 0900-8844, in a SIP 3xx response. However, the digitstring may be part of a message that identifies that the digit stringshould be displayed and/or that a textual message should be displayed toindicate the nature of the call that was made and the nature of thenumber provided.

In one embodiment, the P-CSCF has configurable lists with local androaming partners' emergency service identifiers which indicate peremergency service identifier the handling. When rejecting the request, aconfigurable list of alternate emergency service URIs can be included inthe response, e.g., signaled as part of the SIP Contact header field.These alternative emergency services can be annotated with alphanumericinformation that can be displayed, e.g., when signaled as part of theSIP Contact header field. The alternative emergency services can also beidentified, using an XML body with XML elements and XML attributes, asbeing displayed only if required.

In some cases, the network might reject a request made to a regularemergency center or perhaps a combined PSAP or a combined emergencycentre, where a combined PSAP or a combined emergency centre is a PSAPthat accepts calls for multiple types of emergencies. For example, acombined PSAP or a combined emergency centre might accept calls forpolice emergencies, fire emergencies, ambulance emergencies, and othertypes of emergencies. A request made to a combined emergency centremight include bits, flags or other indicators (such as a PSAP address(e.g., “119” in some countries) or part of an PSAP address) that specifythe emergency response entities to which the request should be routed.For example, if a request is made for fire service and ambulanceservice, the request might include a “fire” flag and an “ambulance”flag. Upon reading these tags, the combined emergency centre can routethe request to the appropriate emergency response entities.

In an embodiment, a UE might send a request to an emergency center orperhaps combined emergency centre and the UE is not aware that therequest is related to an emergency center and for various reasons thenetwork rejects or otherwise does not process the request. In this case,the network might identify the request as related to a combinedemergency centre. The network then sends a message to the UE containinginformation identifying that the request relates to a combined emergencycentre. The UE might then use this information to send the request to acombined emergency centre or combined PSAP or other alternate emergencycentre or PSAP. In some embodiments, the alternate PSAP is in thecircuit switched domain. The information in the message that the networksends to the UE can include information identifying the combinedemergency centre, bits, flags or other indicators that specify theemergency response entities to which the original request was routed.Upon receiving this message, the UE can send an alternate request to thealternate or combined PSAP and can include the bits, flags or otherindicators so that the alternate PSAP can route the alternate request tothe appropriate emergency response entities. The bits, flags or otherindicators may be the bits specified in Table 10.5.135d in 3GPP TS24.008.

More specifically, a network element such as a P-CSCF verifies if therequests that it receives contain emergency service identifiers. TheP-CSCF may determine that a proper emergency call request was made butthat the local network does not support the requested emergency PSAP(e.g., a request to urn:service:sos.gas was made). The P-CSCF may alsodetermine that the UE failed to recognize the request as an emergencycall request. The P-CSCF can then be configured to reject the requestand provide sufficient information for the UE to route the request to analternate answering point since the UE user is of the impression it isreporting a situation that requires attention. However, a PSAP/emergencycentre for that type of emergency is not supported in the network.

Today, in the CS network, Service Categories have been allocated forPolice, Ambulance, Fire Brigade, Marine Guard and Mountain Rescue.However, in the event a 380 (Alternative Service) is returned by theP-CSCF, one of the options the UE has is to initiate an emergency callin the CS domain using appropriate access technology specificprocedures. However, the UE, upon receiving the 380, still does not knowif the original request with the emergency service identifier that wasnot recognized by the UE was destined for a default PSAP, Police PSAP,Ambulance PSAP, Fire Brigade PSAP, combined PSAP, etc.

In an embodiment, in the event the P-CSCF has been configured torecognize the request as for a particular type of emergency, then theP-CSCF informs the UE that the request was for that type of emergency.In addition, if the P-CSCF rejects the request because the requestedemergency type is not supported, the P-CSCF can provide additionalinformation. The UE can be enhanced to handle 380 (Alternative Service)messages for unrecognized emergency requests to particular PSAPs. Whenattempting to connect to a particular PSAP using the CS Domain, amapping to the correct Emergency Category Value (see 3GPP TS 24.008,subclause 10.5.4.33) can be made. The P-CSCF can be enhanced to rejectemergency service requests to unsupported PSAPs, e.g.,urn:service:sos.gas, based on local policy.

The following is an example of an XML body indicating to the UE that anemergency service request was detected and instructing the UE to connectto the determined PSAP.

<ims-3gpp version=“...”> <alternative-service> <type alternate=“tel:119;phone-context=+81urn:service:sos.fire-urn:service:sos.ambulance”> <emergency/> </type><reason/> </alternative-service> </ims-3gpp>

Previous proposals mentioned signaling recognition by the IMS network ofa request to a combined emergency centre and mapping from the signaledvalue representing a combined emergency centre to one or more bitspresented in Table 10.5.135d in 3GPP TS 24.008. 3GPP TS 24.008 isGSM/UMTS specification, and GSM/UMTS supports different regular Setupvs. Emergency Set-up (i.e., without dialed digits). In CDMA, from“IS-2000 release A” onwards, there is also a field calledGLOBAL_EMERGENCY_CALL that can be included in an Origination message tomake such a call independent of a dialed string. The protocol revisionlevel that supports this is 7 and up. Earlier UEs, with a “protocolrevision level currently in use is less than 7”, do not distinguishbetween emergency and normal calls. Thus, such UEs might have to map,say, “tel:119;phone-context=+81” to 119 and dial 119 as a normal call.

Also, CDMA does not support routing to Combined Emergency Centres orSpecialized Emergency Centres (e.g., for “police” only). 3GPP2 onlydocuments how to route to default PSAPs. Thus, in an alternativeembodiment, a CDMA UE detects that the IMS network has determined thatthe original request to the IMS network was for a non-default PSAP. TheCDMA UE might then, rather than sending an emergency call withGLOBAL_EMERGENCY_CALL set to “1” (rather than routing to the defaultPSAP), support one or more of the following: an emergency call withGlobal_Emergency set to “1” and in the address field a phone number: say119, if “the protocol revision level currently in use is NOT less than7”; an emergency call with Global_Emergency set to “0” and in theaddress field a phone number: say 119, if “the protocol revision levelcurrently in use is NOT less than 7”; and/or an emergency call with inthe address field a phone number: say 119, if “the protocol revisionlevel currently in use is less than 7”.

Current proposals add an “alternate attribute” to the existing XMLSchema. In an embodiment, the alternate attribute includes a number ofalternative addresses, one of which (the last element) could be anindicator encoding the need to route the call to a combined emergencycentre by ‘dashing’ together emergency service URNs: e.g.“Urn:service:sos.ambulance-Urn:service:sos.fire”. Alternativeembodiments could encode the alternative addresses differently in theSIP response, e.g., in the Contact header fields or in a separate, newXML body. Another alternative could be a different encoding such thatthe indicator would still be a URN or tel URI or SIP URI. For example,urn:service:sos.fire.ambulance (e.g., ‘dotting’ together the emergencysub types).

An emergency number might be interpreted in different ways in differentcountries. For example, the address “119” might translate topolicy+marine in one country and fire+ambulance in another. If bothcountries have operators that are roaming partners with the home networkof a roaming user, the UE or the network needs to recognize the addressas an emergency request, but the network might not know which 119translation is intended. In an embodiment, in such a situation, thenetwork selects one of the translations after further interaction withthe UE.

Such further interaction includes, for example, the network sendinginformation to the UE indicating that the address is associated withdifferent emergency types in different jurisdictions. Such informationincludes a mapping between the address, a phone context and one or moreoptional emergency identifier types and is known as alternate addressinformation. An emergency identifier type is optional where the phonecontext does not map to an emergency type but non “emergency” or“urgent” alternatives are known.

Alternate address information comprises a mapping between an address, aphone context and one or more optional emergency identifier types. Theaddress indicates the emergency number dialed which could be a telephonenumber such as ‘119’ for example. The phone context indicates a relevantcondition of the UE, such as the location or country the UE is in, andcould be a number or a string such as c+81′, the textual string ‘Japan’,a combination of a number and a string or other information that can beresolved to a location, for example. The textual string (e.g. ‘Japan’)can be received in multiple languages and multiple character encodings,including Japanese and other non ASCII character sets. The emergencyidentifier type (e.g. ‘police’, ‘fire’ or ‘ambulance’ for example) isextendible and indicates the type of emergency service associated withthe address for a given phone context. The country or region where theemergency services apply can be identified using applicable ITU, IANA,ISO codes, however, in some cases certain emergency services areprovided in an area not coinciding with a “country” or region, in whichcase a standard ITU, IANA, ISO code might not have been allocated. SomeITI, IANA, ISO or other codes applicable for encoding locations,countries or regions are extendible, such as ISO 3166-1, and the ISO3166/MA.

Alternate address information may additionally contain a reason element,such as a <reason> XML element (as described in e.g. 3GPP IMS XML bodyas defined in 3GPP TS 24.229) for example. A reason element is populatedwith information that can be presented to a user of a UE to identify,for example, the location, the emergency service types supported and/orthe emergency service numbers. Such a reason element could betransmitted in an enhanced application/3gpp-ims+xml body (as defined in3GPP TS 24.229). The contents of a reason element can be specified inmultiple languages, using the xml:lang attribute. For example, a reasonelement can be represented by the following body (which corresponds toan enhanced XML Schema in 3GPP TS 24.229).

<ims-3gpp version=“2”> <alternative-service> <type><emergency/></type><reason lang=“en”>emergency</reason> <reasonlang=“nl”>noodgeval</reason> </alternative-service> </ims-3gpp>

The network sends such alternate address information to the UE, forexample, as part of the body of a SIP 300 (Multiple Choices) response,in one or more Contact field headers of the SIP 300 (Multiple Choices)response or in another SIP 3xx response (e.g. a SIP 380 (AlternativeService) response).

The following is an example of an XML body included in a response to arequest for an emergency service indicating to the UE that an address(‘119’ for example) is associated with a different, or a combination of,emergency types (‘fire’, ‘ambulance’ or ‘police’ for example) indifferent phone contexts (‘+81’ for example). Note that the emergencytypes are derived from RFC 5031's emergency service URN (i.e.urn:service:sos and its subtypes, police, ambulance, gas, fire, etc.,where <police/> can map to urn:service:sos.police, etc.) Note that theemergency type <sos/> can map to the generic service URNurn:service:sos. Note that <sos/> can map to the dial string “112” or toa GSM/UMTS CS domain emergency call setup with all Emergency ServiceCategory Value bits set to ‘0’ (see Table 10.5.135d/3GPP TS 24.008:Service Category information element) such that the call is routed to anoperator defined default emergency centre or equivalent signaling inother CS domain technologies such as CDMA. Note that <police/> couldalso map to setting bit 1 of the Emergency Service Category Value whenmaking a GSM/UMTS emergency call over the CS domain.

<ims-3gpp version=“...”>  <alternative-service> <type>  <emergency/></type> <reason/> <action>  <alternative><alternativeURI>tel:112;phone-context=+57</alternativeURI> <sos/> </alternative>  <alternative><alternativeURI>tel:123;phone-context=+57</alternativeURI> <ambulance/><fire/> <police/>  </alternative>  <alternative><alternativeURI>tel:119;phone-context=+81</alternativeURI><alternativeURI>tel:119;phone-context=+82</alternativeURI><alternativeURI>tel:119;phone- context=+886</alternativeURI><ambulance/> <fire/>  </alternative>  <alternative><alternativeURI>tel:119;phone-context=+94</alternativeURI><alternativeURI>tel:119;phone- context=+1876</alternativeURI> <police/> </alternative>  <alternative><alternativeURI>tel:119;phone-context=+57</alternativeURI><alternativeURI>tel:119;phone-context=+86</alternativeURI> <fire/> </alternative>  <alternative><alternativeURI>tel:119;phone-context=+62</alternativeURI><alternativeURI>tel:118;phone-context=+62</alternativeURI> <ambulance/> </alternative> </action>  </alternative-service> </ims-3gpp>

The above exemplary XML body indicates that the address ‘119’ can betranslated to a different emergency type in a different jurisdiction.For example, the address ‘119’ is associated with ‘fire’ and ‘ambulance’emergency services when the UE is in a jurisdiction having a phonecontext of ‘+81’ (Japan) or ‘+82’ (Korea). The address ‘119’ isalternatively associated with ‘police’ emergency services when the UE isin a jurisdiction having a phone context of ‘+94’ (Sri Lanka).

If a country code or location code is included in an emergency servicerequest which can be mapped to multiple emergency service types, it isassumed that the handset specifically intends for the request to berouted to the emergency service type associated to the emergency serviceaddress in the indicated country or region.

In another embodiment, the UE or network are configured to select orreduce the alternatives in the response and to remove some of the lessprobable possibilities. Such selection or reduction can be achievedbased on the current network of a UE, the home network of the UE, thenationality of the user of the UE, or past travel plans of the user ofthe UE for example. A UE which performs selection or reduction, couldinclude a policy which hard codes a mapping between an address, anemergency type and phone context, thereby enabling the UE to explicitlyselect the intended emergency type when making an emergency call overthe CS domain or PS domain. On the PS domain, an emergency type can beeither indicated per a RFC 5031 URN or per a TEL URL including a countryor region indicator such as ‘phone context’. An emergency type selectionfunction on the UE could be further enhanced if the UE is aware of thecountry or region it is in and if a locally stored or received mappingof emergency types, location indicators and emergency call addresses ispresent. The emergency type selection function could then determine thatthat in certain countries or regions a certain mapping does or does NOTapply, or the mapping applies universally (e.g. for UMTS/GSM handsetsthe number “112” can map to a GSM/UMTS CS domain emergency call setupwith all Emergency Service Category Value bits set to ‘0’ (see Table10.5.135d/3GPP TS 24.008: Service Category information element)).

Such further interaction between the network and the UE to select atranslation also includes, for example, placing choices for thetranslation in a textual field to be displayed on the UE (such as the<reason> element in the 3GPP IMS XML body). The UE user could thenselect one of the choices, the selection could be transmitted to thenetwork, and the network could translate the emergency number based onthe selection. Alternatively, the network could make the selection inthe following order: map the address (e.g., 119) as defined in the homenetwork; if the address is not defined in the home network, map theaddress as defined in the current visited network, if the address is notdefined in the current visited network, map the address as defined forroaming partners or route the call to the default or most capable PSAP.Alternatively, the request can always be routed to the default or mostcapable PSAP.

A similar problem can occur for the UE when it attempts to recognize thedialed address as an emergency identifier. In an embodiment, the UE isconfigured with one translation to prevent this problem from occurring.Alternatively, the UE can interact with the user to select a desiredtranslation. Alternatively, the UE can be configured to route the callto the default or most capable PSAP. Alternatively, the UE could routethe call based on the network it is attached to and could map the digitsaccording to that network's rules. The UE could also interact with thenetwork and use any advice it gets.

In yet another embodiment, the P-CSCF will not reject the request for anunsupported emergency service type (such as urn:service:sos.poison) butprepare it for forwarding to the user's home network S-CSCF using normalprocedures (as opposed to forwarding it to an E-CSCF). The user's homenetwork's S-SCSF should then be configured to handle the unrouteableRequest URI value. The IMS network may also be configured to takeaccount of roaming users requesting a session withurn:service:sos.police, such that the service requested by a UE whichmay be half way around the world, can still be handled in a timely andeffective manner. The IMS network could provide an indication in a SIPmessage to the UE that the call has been determined to not be anemergency call and that its handling will be different. The indicationcould be a flag and/or alphanumeric information. Possible encodings ofthis type of indicator are given in this document.

Returning to the case where an IMS network component determines that theUE 110 has initiated an emergency call without recognizing it as such,in some embodiments the IMS network 120 includes the emergency callindicator 160 in a SIP response that is sent to the UE 110. In thiscase, the indicator 160 is provided during the call setup signalingphase. In other embodiments, the emergency call indicator 160 isincluded in a message that originates at the PSAP 130. The IMS network120 then transfers the message from the PSAP 130 to the UE 110.

In other embodiments, if a component in the IMS network 120 includes theemergency call indicator 160 in the SIP response that is sent to the UE110, the UE 110 can abort the current signaling and initiate regularemergency call setup procedures, which may involve originating a callover a Circuit Switched network, if capable and available, or afterinitiating emergency registration procedures, or sending a SIP INVITErequest containing an indicator indicating that the SIP INVITE requestis an emergency-related call request and containing emergency-relatedinformation about itself.

Information that is similar to the information 180 that the UE 110includes in the SIP message 170 might be included by the UE 110 in amessage sent under different circumstances. This is illustrated in FIG.2, where the UE 110, the IMS network 120, and the PSAP 130 are againpresent. However, in this case the PSAP 130 initiates a callback to theUE 110. As is well known in the art, after an emergency call isterminated, the PSAP 130 may place a callback to the UE 110 for variousreasons. For example, if the emergency call appears to have terminatedabnormally, the PSAP 130 might call the UE 110 back to determine if theUE user wishes to convey any additional information. Alternatively, thePSAP 130 might call the user back to ask for information that wasinadvertently not requested in the initial call. Other reasons for acallback from the PSAP 130 to an emergency caller after the terminationof an emergency call may be familiar to one of skill in the art.

The PSAP 130 might initiate the callback by sending a SIP INVITE message210, or a similar message, to the UE 110 via the IMS network 120. In anembodiment, the SIP INVITE message 210 contains an indicator 220 thatindicates that the SIP INVITE message 210 is related to an emergencycallback. The indicator 220 might be substantially similar to theindicator 160 of FIG. 1 or might be some other type of indicator. The UE110 can recognize that the indicator 220 is an indication of anemergency callback from the PSAP 130 and can respond to the indicator220 appropriately by invoking emergency callback functionality, subjectto policies. In an embodiment, the response of the UE 110 to receivingthe indicator 220 is substantially similar to the response that the UE110 had upon receiving the indicator 160 of FIG. 1.

For example, one action that the UE 110 might take upon recognizing theindicator 220 is visually or audibly indicating the nature of thesession to the user. That is, the UE 110 might alert the user that theincoming call is an emergency callback. The alert might be a messagethat appears on the display screen of the UE 110 or some other type ofindication of the nature of the call. Other actions taken by the UE 110can involve transmitting a SIP 2xx or 1xx response (e.g. SIP 200(OK)response) 230, or a similar message, that includes information 240 aboutthe UE 110, subject to policies. Alternatively, due to limitations inSIP, the information 240 can be transmitted over several SIP messages ornetwork messages (e.g., UE-provided IP-CAN identity information may notbe completely reliable and hence a mechanism based on network provision(e.g., using Policy Control and Charging (PCC)) can provide suchinformation) or within a target refresh request such as a SIP re-INVITErequest or an UPDATE request or partially in a SIP PRACK request. Theinformation 240 might be substantially similar to the information 180that the UE 110 provided upon receiving the indicator 160 of FIG. 1.

One piece of the information 240 that the UE 110 might send to the PSAP130 is the UE's public user identity or some other identifying symbol.Another piece of information 240 that the UE 110 might transmit in theSIP 200OK message 230 is the type of access that the UE 110 used for theoriginal emergency call. For example, if the emergency call was madeover a wireless LAN, the UE 110 might include that fact in theinformation 240, as well as a cell ID, a line ID, and/or a wireless LANaccess node ID.

If the UE 110 is aware of its geographic location, through the use of aGPS system for example, the UE 110 can include its location as anotherpiece of the information 240. If the UE 110 is not aware of itsgeographic location, location-related data is not included in theinformation 240. If a GRUU is associated with the UE 110, the UE's GRUUcan be included as another piece of the information 240.

In an alternative embodiment, the PSAP 130 might setup a CircuitSwitched (CS) call and a CS gateway might then convert the call and thesignaling in packet switched technology if the CS call is routed to theCS gateway. Triggered by the incoming call from the PSAP 130, the CSgateway might initiate the callback over packet switched technology bysending a SIP INVITE message 210, or a similar message, to the UE 110via the IMS network 120.

FIG. 3 illustrates an embodiment of a method 300 for a UE to respond toan emergency-related message sent to the UE. In block 310, the UEreceives a message containing an indicator indicating that anemergency-related call has been placed. In some cases, theemergency-related call may have been placed by the UE without the UEbeing aware that the call was related to an emergency. In other cases,the emergency-related call might be a callback from a PSAP to the UE inresponse to a previous emergency call from the UE. In block 320, the UErecognizes the indicator as an indication that its first message(initial SIP request for a dialog or standalone transaction, or unknownmethod or similar message) is related to an emergency. Optionally, inblock 330, the UE provides a visual, audible, or other indication to theUE user that the emergency-related call is related to an emergency. Inblock 340, the UE sends a message containing emergency-relatedinformation about itself.

The disclosure described herein might be implemented as one or moremodifications to the Third Generation Partnership Project (3GPP)Technical Specification (TS) 24.229 “Internet Protocol (IP) MultimediaCall Control Protocol Based on Session Initiation Protocol (SIP) andSession Description Protocol (SDP); Stage 3”. Proposed additions andmodifications to TS 24.229, according to various embodiments of thepresent disclosure, are provided below.

The following addition to 3GPP TS 24.229 applies to the initial INVITErequest in the UE-originating case of a call initiation:

In the event the UE receives a 380 (Alternative Service) response to anINVITE request the response containing a XML, body that includes an<alternative service> element with the <type> child element's“alternate” attribute containing one or more emergency service URIs, theUE can attempt a normal call as described in subclause 5.1.3.1 using aemergency service URI or using call setup according to the proceduresdescribed in 3GPP TS 24.008 [8]. The behavior of the UE isimplementation specific if the <type> child element's “alternate”attribute is absent or contains no emergency service URIs.

The following modification to 3GPP TS 24.229 applies to generalemergency service:

The P-CSCF shall store a configurable list of local emergency serviceidentifiers, i.e. emergency numbers and the emergency service URN, whichare valid for the operator to which the P-CSCF belongs to. In additionto that, the P-CSCF shall store a configurable list of roaming partners'emergency service identifiers. The configurable lists with local androaming partners' emergency service identifiers shall indicate peremergency service identifier the handling. When the handling indicatedthat the request shall be rejected, a configurable list of alternateemergency service URIs may be included in the response.

The following addition to 3GPP TS 24.229 applies to the generaltreatment for all dialogs and standalone transactions excluding theREGISTER method after emergency registration:

If the P-CSCF detects that the Request-URI of the initial request for adialog, or a standalone transaction, or an unknown method matches anunsupported type of emergency in the VPLMN or HPLMN's emergency serviceidentifiers, the P-CSCF shall:

-   -   shall respond to the INVITE request with a 380 (Alternative        Service) response;    -   shall assume that the UE supports version 1 of the XML Schema        for the IM CN subsystem XML body if support for the 3GPP IMS XML        body in the Accept header is not indicated; and    -   shall include in the 380 (Alternative Service) response:        -   a Content-Type header field with the value set to associated            MIME type of the 3GPP IMS XML body as described in subclause            7.6.1.    -   The body shall contain:    -   a) an <alternative-service> element, set to the parameters of        the alternative service;    -   b) if the Accept header indicates support for version 2 of the        XML Schema for the IM CN subsystem XML body        -   then, a <type> child element with an “alternate” attribute            set to a list of alternate emergency service URIs,        -   otherwise, a <type> child element, set to “emergency”;    -   c) a <reason> child element, set to an operator configurable        reason.

The following, alternative addition to 3GPP TS 24.229 applies to thegeneral treatment for all dialogs and standalone transactions excludingthe REGISTER method after emergency registration:

If the P-CSCF detects that the Request-URI of the initial request for adialog, or a standalone transaction, or an unknown method matches anunsupported type of emergency in the VPLMN or HPLMN's emergency serviceidentifiers, the P-CSCF shall:

-   -   shall respond to the INVITE request with a 380 (Alternative        Service) response;    -   shall assume that the UE supports version 1 of the XML Schema        for the IM CN subsystem XML, body if support for the 3GPP IMS        XML body in the Accept header is not indicated; and    -   shall include in the 380 (Alternative Service) response:        -   a Content-Type header field with the value set to associated            MIME type of the 3GPP IMS XML body as described in subclause            7.6.1.    -   The body shall contain:    -   a) an <alternative-service> element, set to the parameters of        the alternative service;    -   b) a <type> child element with an “alternate” attribute set to a        list of alternate emergency service URIs,    -   c) a <reason> child element, set to an operator configurable        reason.

The following modification to 3GPP TS 24.229 applies to the generaltreatment for all dialogs and standalone transactions excluding theREGISTER method for a non-emergency registration:

If the P-CSCF receives an initial request for a dialog, or a standalonetransaction, or an unknown method, for a registered user the P-CSCFshall inspect the Request URI independent of values of possible entriesin the received Route headers for known emergency service identifiers,i.e. emergency numbers and the emergency service URN from theseconfigurable lists. If the P-CSCF detects that the Request-URI of theinitial request for a dialog, or a standalone transaction, or an unknownmethod matches one of the emergency service identifiers in any of theselists, the P-CSCF shall:

-   -   0) determine the geographical location of the UE. Access        technology specific procedures are described in each access        technology specific annex. If the P-CSCF is not capable to        handle emergency sessions or due to local policy does not handle        emergency sessions or only handles certain type of emergency        session request or the IP-CAN to which the UE is attached or the        UE is roaming or the P-CSCF is in a different network than the        UE's home operator's network, then the P-CSCF:        -   shall reject the request by returning a 380 (Alternative            Service) response to the UE;        -   shall assume that the UE supports version 1 of the XML            Schema for the IM CN subsystem XML body if support for the            3GPP IMS XML body in the Accept header is not indicated; and        -   shall include in the 380 (Alternative Service) response:            -   a Content-Type header field with the value set to                associated MIME type of the 3GPP IMS XML body as                described in subclause 7.6.1.        -   The body shall contain:        -   a) an <alternative-service> element, set to the parameters            of the alternative service;        -   b) if the Accept header indicates support for version 2 of            the XML Schema for the IM CN subsystem XML body            -   then, a <type> child element with an “alternate”                attribute set to a list of alternate emergency service                URIs, and                -   if the initial request for a dialog, or standalone                    transaction, or unknown method was for a supported                    type of emergency, the <type> child element is set                    to “emergency” to indicate that it was a supported                    emergency call,            -   otherwise, a <type> child element, set to “emergency”;        -   c) a <reason> child element, set to an operator configurable            reason; and        -   d) an <action> child element, set to            “emergency-registration” if the request included an            emergency service URN in the Request-URI.    -   NOTE 1: Roaming is when a UE is in a geographic area that is        outside the serving geographic area of the home IM CN subsystem.    -   NOTE 1a: “sip:911@example.com,user=phone” could be an alternate        emergency service URI. “urn:service:sos animal-control” could be        an unsupported type of emergency call.    -   NOTE 2: Emergency service URN in the request-URI indicates for        the network that the emergency call attempt is recognized by the        UE.

The following alternative modification to 3GPP TS 24.229 applies to thegeneral treatment for all dialogs and standalone transactions excludingthe REGISTER method for a non-emergency registration:

If the P-CSCF receives an initial request for a dialog, or a standalonetransaction, or an unknown method, for a registered user the P-CSCFshall inspect the Request URI independent of values of possible entriesin the received Route headers for known emergency service identifiers,i.e. emergency numbers and the emergency service URN from theseconfigurable lists. If the P-CSCF detects that the Request-URI of theinitial request for a dialog, or a standalone transaction, or an unknownmethod matches one of the emergency service identifiers in any of theselists, the P-CSCF shall:

-   -   0) determine the geographical location of the UE. Access        technology specific procedures are described in each access        technology specific annex. If the P-CSCF is not capable to        handle emergency sessions or due to local policy does not handle        emergency sessions or only handles certain type of emergency        session request or the IP-CAN to which the UE is attached or the        UE is roaming or the P-CSCF is in a different network than the        UE's home operator's network, then the P-CSCF:        -   shall reject the request by returning a 380 (Alternative            Service) response to the UE;        -   shall assume that the UE supports version 1 of the XML            Schema for the IM CN subsystem XML, body if support for the            3GPP IMS XML body in the Accept header is not indicated; and        -   shall include in the 380 (Alternative Service) response:            -   a Content-Type header field with the value set to                associated MIME type of the 3GPP IMS XML body as                described in subclause 7.6.1.        -   The body shall contain:        -   a) an <alternative-service> element, set to the parameters            of the alternative service;        -   b) a <type> child element with an “alternate” attribute set            to a list of alternate emergency service URIs, and            -   if the initial request for a dialog, or standalone                transaction, or unknown method was for a supported type                of emergency, the <type> child element is set to                “emergency” to indicate that it was a supported                emergency call;        -   c) a <reason> child element, set to an operator configurable            reason; and        -   d) an <action> child element, set to            “emergency-registration” if the request included an            emergency service URN in the Request-URI.    -   NOTE 1: Roaming is when a UE is in a geographic area that is        outside the serving geographic area of the home IM CN subsystem.    -   NOTE 2: Emergency service URN in the request-URI indicates for        the network that the emergency call attempt is recognized by the        UE.

The following modification to 3GPP TS 24.229 applies to abnormal cases:

If the IM CN subsystem to where the P-CSCF belongs to is not capable tohandle emergency sessions or due to local policy does not handleemergency sessions or only handles certain type of emergency sessionrequest or does not support emergency sessions for either thegeographical location of the UE is located or the IP-CAN to which the UEis attached, the P-CSCF shall not forward the INVITE request. TheP-CSCF:

-   -   shall respond to the INVITE request with a 380 (Alternative        Service) response;    -   shall assume that the UE supports version 1 of the XML Schema        for the IM CN subsystem XML body if support for the 3GPP IMS XML        body in the Accept header is not indicated; and    -   shall include in the 380 (Alternative Service) response:        -   a Content-Type header field with the value set to associated            MIME type of the 3GPP IMS XML body as described in subclause            7.6.1.    -   The body shall contain:    -   a) an <alternative-service> element, set to the parameters of        the alternative service;    -   b) if the Accept header indicates support for version 2 of the        XML Schema for the IM CN subsystem XML body        -   then, a <type> child element with an “alternate” attribute            set to a list of alternate emergency service URIs, and            -   if the initial request for a dialog, or standalone                transaction, or unknown method was for a supported type                of emergency, the <type> child element is set to                “emergency” to indicate that it was a supported                emergency call,        -   otherwise, a <type> child element, set to “emergency”;    -   c) a <reason> child element, set to an operator configurable        reason; and    -   d) an <action> child element, set to “emergency-registration” if        the request included an emergency service URN in the        Request-URI.    -   NOTE 1: Emergency service URN in the request-URI indicates for        the network that the emergency call attempt is recognized by the        UE.    -   NOTE 1a: “sip:911@example.com,user=phone” could be an alternate        emergency service URI. “urn:service:sos animal-control” could be        an unsupported type of emergency call.    -   NOTE 2: Some networks only allow session requests with a        Request-URI containing an emergency service URN, i.e. a service        URN with a top-level service type of “sos” as specified in        draft-ietf-ecrit-service-urn [69].

The following alternative modification to 3GPP TS 24.229 applies toabnormal cases:

If the IM CN subsystem to where the P-CSCF belongs to is not capable tohandle emergency sessions or due to local policy does not handleemergency sessions or only handles certain type of emergency sessionrequest or does not support emergency sessions for either thegeographical location of the UE is located or the IP-CAN to which the UEis attached, the P-CSCF shall not forward the INVITE request. TheP-CSCF:

-   -   shall respond to the INVITE request with a 380 (Alternative        Service) response;    -   shall assume that the UE supports version 1 of the XML Schema        for the IM CN subsystem XML, body if support for the 3GPP IMS        XML body in the Accept header is not indicated; and    -   shall include in the 380 (Alternative Service) response:        -   a Content-Type header field with the value set to associated            MIME type of the 3GPP IMS XML body as described in subclause            7.6.1.    -   The body shall contain:    -   a) an <alternative-service> element, set to the parameters of        the alternative service;    -   b) a <type> child element with an “alternate” attribute set to a        list of alternate emergency service URIs, and        -   if the initial request for a dialog, or standalone            transaction, or unknown method was for a supported type of            emergency, the <type> child element is set to “emergency” to            indicate that it was a supported emergency call;    -   c) a <reason> child element, set to an operator configurable        reason; and    -   d) an <action> child element, set to “emergency-registration” if        the request included an emergency service URN in the        Request-URI.    -   NOTE 1: Emergency service URN in the request-URI indicates for        the network that the emergency call attempt is recognized by the        UE.    -   NOTE 2: Some networks only allow session requests with a        Request-URI containing an emergency service URN, i.e. a service        URN with a top-level service type of “sos” as specified in        draft-ietf-ecrit-service-urn [69].

The following modification might be made to the 3GPP IM CN subsystem XMLbody XML Schema to implement one or more of the embodiments disclosedherein:

<xs:complexType name=“tType”> <xs:sequence> <xs:element name=“emergency”minOccurs=“0” maxOccurs=“1”> <xs:complexType/> </xs:element> <xs:anynamespace=“##any” processContents=“lax” minOccurs=“0”maxOccurs=“unbounded”/> </xs:sequence> <xs:attribute name=“alternate”type=“anyURIlist”/> <xs:anyAttribute/> </xs:complexType>

-   -   The <action> element contains the “alternate” attribute and only        the value “emergency-registration” in the present document. The        “alternate” attribute can be set to a list of alternate        emergency service URIs.

The following two additions to 3GPP TS 24.229 apply to genericprocedures applicable to all methods excluding the REGISTER method:

Upon generating an initial request for a dialog, or a standalonetransaction, or an unknown method, excluding ACK and CANCEL, the UEshall include the Accept header with “application/sdp”, the MIME typeassociated with the 3GPP IMS XML body (see subclause 7.6.1) and anyother MIME type the UE is willing and capable to accept.In the event the UE receives a 380 (Alternative Service) response to aninitial request for a dialog, or a standalone transaction, or an unknownmethod, the response including an IM CN subsystem XML body as describedin subclause 7.6 that includes an <alternative service> element with the<type> child element set to “emergency”, the UE shall attempt anemergency call as described in subclause 5.1.6.If 1xx or 2xx response to an initial request for a dialog, or astandalone transaction, or an unknown method, contains an emergencysession indicator, then the UE shall send a re-INVITE request methodaccording to RFC 3261 [26], and:

-   -   1) the UE shall indicate the nature of the session to the user;    -   NOTE 17 the UE does not change the From header to include a        public user identity or the tel URI associated with the public        user identity, in this version of the specification.    -   2) if available to the UE, and if defined for the access type as        specified in subclause 7.2A.4, the UE shall include a        P-Access-Network-Info header and it shall contain a location        identifier such as the cell id, line id or the identity of the        I-WLAN access node;    -   NOTE 18: The IMS emergency specification in 3GPP TS 23.167 [4B]        describes several methods how the UE can get its location        information from the access network or from a server. Such        methods are not in the scope of this specification.    -   3) the UE shall insert a P-Preferred-Identity that includes the        public user identity or the tel URI associated with the public        user identity as described in subclause 4.2;    -   4) if the UE has its location information available, then the UE        shall include it in the following way:        -   if the UE is aware of the URI that points to where the UE's            location is stored, include the URI in the Geolocation            header in accordance with draft-ietf-sip-location-conveyance            [89]; or        -   if the geographical location information of the UE is            available to the UE, include its geographical location            information as PIDF location object in accordance with RFC            4119 [90] and include the location object in a message body            with the content type application/pidf+xml in accordance            with draft-ietf-sip-location-conveyance [89]. The            Geolocation header is set to a Content ID in accordance with            draft-ietf-sip-location-conveyance [89]; and    -   5) if the UE has no geographical location information available,        the UE shall not include any geographical location information        as specified in draft-ietf-sip-location-conveyance [89]; and    -   6) if a public GRUU value (pub-gruu) has been saved associated        with the public user identity and the UE does not indicate        privacy of the P-Asserted-Identity, then the UE shall insert the        public GRUU (pub-gruu) value in the Contact header as specified        in draft-ietf-sip-gruu [93]; otherwise the UE shall include the        protected server port in the address in the Contact header.    -   NOTE 19 according to RFC 3261 [26], a reINVITE request can not        be sent while another INVITE transaction is in progress in        either direction.    -   NOTE 20 it is not necessary for this reINVITE request to change        the session parameters.    -   NOTE 21: It is suggested that UE's only use the option of        providing a URI when the domain part belongs to the current        P-CSCF or S-CSCF provider. This is an issue on which the network        operator needs to provide guidance to the end user. A URI that        is only resolvable to the UE which is making the emergency call        is not desirable.    -   NOTE 22: During the dialog, the points of attachment to the        IP-CAN of the UE can change (e.g. UE connects to different        cells). The UE will populate the P-Access-Network-Info header in        any request (except ACK requests and CANCEL requests) or        response (except CANCEL responses) within a dialog with the        current point of attachment to the IP-CAN (e.g. the current cell        information).

Applying privacy, including removing location and access networkinformation, if the PSAP is within the network's trust domain, can beperformed by IMS network elements such as E-CSCF, IBCF or others. It maybe preferred that “session” privacy is requested (i.e. Privacy headerfield set to include the value “session” since P-Access-Network-Infoheader field is present in most SIP messages). It may be preferred thatthe E-CSCF receives location such that it can determine the mostapplicable PSAP and use it in routing the request to the PSAP oremergency response centre. Privacy requirements according to RFC 4244may also apply but at present no procedures foresee including historyinformation in an emergency services request. The following twoadditions to 3GPP TS 24.229 apply to Procedures at the E-CSCF:

-   -   When the E-CSCF receives a request for a dialog requesting        privacy or standalone transaction requesting privacy or any        request or response related to a UE-originated dialog requesting        privacy or standalone transaction requesting privacy, and if        local operator policy allows user request for suppression of        public user identifiers and location information, the E-CSCF        shall:        -   apply any privacy required by RFC 3323 [33] relating to            privacy and RFC 3325 [34] to the P-Asserted-Identity header;        -   if present, remove the P-ACCESS-NETWORK-INFO header field;        -   if present, remove the location object from the message's            body and remove the content type application/pidf+xml from            the Content-Type header field;        -   if present, remove the Geolocation header field.    -   NOTE: Operator policies (e.g. requirements for support of        emergency communications) may over-ride the user request for        suppression.    -   6) select, based on location information and optionally type of        emergency service:        -   a PSAP connected to the IM CN subsystem network and add the            PSAP URI to the topmost Route header; or    -   NOTE 3: If the user did not request privacy, the E-CSCF conveys        the P-Access-Network-Info header containing the location        identifier, if defined for the access type as specified in        subclause 7.2A.4, to the PSAP.    -   a PSAP in the PSTN, add the BGCF URI to the topmost Route header        and add a PSAP URI in tel URI format to the Request-URI with an        entry used in the PSTN/CS domain to address the PSAP;    -   NOTE 4: If the user did not request privacy, the E-CSCF conveys        the P-Access-Network-Info header containing the location        identifier, if defined for the access type as specified in        subclause 7.2A.4, towards the MGCF. The MGCF can translate the        location information if included in INVITE (i.e. both the        geographical location information in PIDF-LO and the location        identifier in the P-Access-Network-Info header) into ISUP        signalling, see 3GPP TS 29.163 [11B].    -   NOTE 5: The E-CSCF can request location information and routeing        information from the LRF. The E-CSCF can for example send the        location identifier to LRF and LRF maps the location identifier        into the corresponding geographical location information that        LRF sends to E-CSCF. The LRF can invoke an RDF to convert the        location information into a proper PSAP/EC URI. Both the        location information and the PSAP URI are returned to the        E-CSCF.    -   NOTE 6: The way the E-CSCF determines the next hop address when        the PSAP address is a tel URI is implementation dependent.    -   7) If the user did not request privacy and if the E-CSCF        receives a reference number from the LRF the E-CSCF shall        include the reference number in the P-Asserted-Identity header;    -   NOTE 7: The reference number is used in the communication        between the PSAP and LRF.

FIG. 4 illustrates a wireless communications system including anembodiment of the UE 110. The UE 110 is operable for implementingaspects of the disclosure, but the disclosure should not be limited tothese implementations. Though illustrated as a mobile phone, the UE 110may take various forms including a wireless handset, a pager, a personaldigital assistant (PDA), a portable computer, a tablet computer, or alaptop computer. Many suitable devices combine some or all of thesefunctions. In some embodiments of the disclosure, the UE 110 is not ageneral purpose computing device like a portable, laptop or tabletcomputer, but rather is a special-purpose communications device such asa mobile phone, wireless handset, pager, or PDA. In another embodiment,the UE 110 may be a portable, laptop or other computing device. The UE110 may support specialized activities such as gaming, inventorycontrol, job control, and/or task management functions, and so on.

The UE 110 includes a display 402. The UE 110 also includes atouch-sensitive surface, a keyboard or other input keys generallyreferred as 404 for input by a user. The keyboard may be a full orreduced alphanumeric keyboard such as QWERTY, Dvorak, AZERTY, andsequential types, or a traditional numeric keypad with alphabet lettersassociated with a telephone keypad. The input keys may include atrackwheel, an exit or escape key, a trackball, and other navigationalor functional keys, which may be inwardly depressed to provide furtherinput function. The UE 110 may present options for the user to select,controls for the user to actuate, and/or cursors or other indicators forthe user to direct. The UE 110 may further accept data entry from theuser, including numbers to dial or various parameter values forconfiguring the operation of the UE 110. The UE 110 may further executeone or more software or firmware applications in response to usercommands. These applications may configure the UE 110 to perform variouscustomized functions in response to user interaction. Additionally, theUE 110 may be programmed and/or configured over-the-air, for examplefrom a wireless base station, a wireless access point, or a peer UE 110.

Among the various applications executable by the UE 110 are a webbrowser, which enables the display 402 to show a web page. The web pagemay be obtained via wireless communications with a wireless networkaccess node, a cell tower, a peer UE 110, or any other wirelesscommunication network or system 400. The network 400 is coupled to awired network 408, such as the Internet. Via the wireless link and thewired network, the UE 110 has access to information on various servers,such as a server 410. The server 410 may provide content that may beshown on the display 402. Alternately, the UE 110 may access the network400 through a peer UE 110 acting as an intermediary, in a relay type orhop type of connection.

FIG. 5 shows a block diagram of the UE 110. While a variety of knowncomponents of UEs 110 are depicted, in an embodiment a subset of thelisted components and/or additional components not listed may beincluded in the UE 110. The UE 110 includes a digital signal processor(DSP) 502 and a memory 504. As shown, the UE 110 may further include anantenna and front end unit 506, a radio frequency (RF) transceiver 508,an analog baseband processing unit 510, a microphone 512, an earpiecespeaker 514, a headset port 516, an input/output interface 518, aremovable memory card 520, a universal serial bus (USB) port 522, ashort range wireless communication sub-system 524, an alert 526, akeypad 528, a liquid crystal display (LCD), which may include a touchsensitive surface 530, an LCD controller 532, a charge-coupled device(CCD) camera 534, a camera controller 536, and a global positioningsystem (GPS) sensor 538. In an embodiment, the UE 110 may includeanother kind of display that does not provide a touch sensitive screen.In an embodiment, the DSP 502 may communicate directly with the memory504 without passing through the input/output interface 518.

The DSP 502 or some other form of controller or central processing unitoperates to control the various components of the UE 110 in accordancewith embedded software or firmware stored in memory 504 or stored inmemory contained within the DSP 502 itself. In addition to the embeddedsoftware or firmware, the DSP 502 may execute other applications storedin the memory 504 or made available via information carrier media suchas portable data storage media like the removable memory card 520 or viawired or wireless network communications. The application software maycomprise a compiled set of machine-readable instructions that configurethe DSP 502 to provide the desired functionality, or the applicationsoftware may be high-level software instructions to be processed by aninterpreter or compiler to indirectly configure the DSP 502.

The antenna and front end unit 506 may be provided to convert betweenwireless signals and electrical signals, enabling the UE 110 to send andreceive information from a cellular network or some other availablewireless communications network or from a peer UE 110. In an embodiment,the antenna and front end unit 506 may include multiple antennas tosupport beam forming and/or multiple input multiple output (MIMO)operations. As is known to those skilled in the art, MIMO operations mayprovide spatial diversity which can be used to overcome difficultchannel conditions and/or increase channel throughput. The antenna andfront end unit 506 may include antenna tuning and/or impedance matchingcomponents, RF power amplifiers, and/or low noise amplifiers.

The RF transceiver 508 provides frequency shifting, converting receivedRF signals to baseband and converting baseband transmit signals to RF.In some descriptions a radio transceiver or RF transceiver may beunderstood to include other signal processing functionality such asmodulation/demodulation, coding/decoding, interleaving/deinterleaving,spreading/despreading, inverse fast Fourier transforming (IFFT)/fastFourier transforming (FFT), cyclic prefix appending/removal, and othersignal processing functions. For the purposes of clarity, thedescription here separates the description of this signal processingfrom the RF and/or radio stage and conceptually allocates that signalprocessing to the analog baseband processing unit 510 and/or the DSP 502or other central processing unit. In some embodiments, the RFTransceiver 508, portions of the Antenna and Front End 506, and theanalog baseband processing unit 510 may be combined in one or moreprocessing units and/or application specific integrated circuits(ASICs).

The analog baseband processing unit 510 may provide various analogprocessing of inputs and outputs, for example analog processing ofinputs from the microphone 512 and the headset 516 and outputs to theearpiece 514 and the headset 516. To that end, the analog basebandprocessing unit 510 may have ports for connecting to the built-inmicrophone 512 and the earpiece speaker 514 that enable the UE 110 to beused as a cell phone. The analog baseband processing unit 510 mayfurther include a port for connecting to a headset or other hands-freemicrophone and speaker configuration. The analog baseband processingunit 510 may provide digital-to-analog conversion in one signaldirection and analog-to-digital conversion in the opposing signaldirection. In some embodiments, at least some of the functionality ofthe analog baseband processing unit 510 may be provided by digitalprocessing components, for example by the DSP 502 or by other centralprocessing units.

The DSP 502 may perform modulation/demodulation, coding/decoding,interleaving/deinterleaving, spreading/despreading, inverse fast Fouriertransforming (IFFT)/fast Fourier transforming (FFT), cyclic prefixappending/removal, and other signal processing functions associated withwireless communications. In an embodiment, for example in a codedivision multiple access (CDMA) technology application, for atransmitter function the DSP 502 may perform modulation, coding,interleaving, and spreading, and for a receiver function the DSP 502 mayperform despreading, deinterleaving, decoding, and demodulation. Inanother embodiment, for example in an orthogonal frequency divisionmultiplex access (OFDMA) technology application, for the transmitterfunction the DSP 502 may perform modulation, coding, interleaving,inverse fast Fourier transforming, and cyclic prefix appending, and fora receiver function the DSP 502 may perform cyclic prefix removal, fastFourier transforming, deinterleaving, decoding, and demodulation. Inother wireless technology applications, yet other signal processingfunctions and combinations of signal processing functions may beperformed by the DSP 502.

The DSP 502 may communicate with a wireless network via the analogbaseband processing unit 510. In some embodiments, the communication mayprovide Internet connectivity, enabling a user to gain access to contenton the Internet and to send and receive e-mail or text messages. Theinput/output interface 518 interconnects the DSP 502 and variousmemories and interfaces. The memory 504 and the removable memory card520 may provide software and data to configure the operation of the DSP502. Among the interfaces may be the USB interface 522 and the shortrange wireless communication sub-system 524. The USB interface 522 maybe used to charge the UE 110 and may also enable the UE 110 to functionas a peripheral device to exchange information with a personal computeror other computer system. The short range wireless communicationsub-system 524 may include an infrared port, a Bluetooth interface, anIEEE 802.11 compliant wireless interface, or any other short rangewireless communication sub-system, which may enable the UE 110 tocommunicate wirelessly with other nearby UEs and/or wireless basestations.

The input/output interface 518 may further connect the DSP 502 to thealert 526 that, when triggered, causes the UE 110 to provide a notice tothe user, for example, by ringing, playing a melody, or vibrating. Thealert 526 may serve as a mechanism for alerting the user to any ofvarious events such as an incoming call, a new text message, and anappointment reminder by silently vibrating, or by playing a specificpre-assigned melody for a particular caller.

The keypad 528 couples to the DSP 502 via the interface 518 to provideone mechanism for the user to make selections, enter information, andotherwise provide input to the UE 110. The keyboard 528 may be a full orreduced alphanumeric keyboard such as QWERTY, Dvorak, AZERTY andsequential types, or a traditional numeric keypad with alphabet lettersassociated with a telephone keypad. The input keys may include atrackwheel, an exit or escape key, a trackball, and other navigationalor functional keys, which may be inwardly depressed to provide furtherinput function. Another input mechanism may be the LCD 530, which mayinclude touch screen capability and also display text and/or graphics tothe user. The LCD controller 532 couples the DSP 502 to the LCD 530.

The CCD camera 534, if equipped, enables the UE 110 to take digitalpictures. The DSP 502 communicates with the CCD camera 534 via thecamera controller 536. In another embodiment, a camera operatingaccording to a technology other than Charge Coupled Device cameras maybe employed. The GPS sensor 538 is coupled to the DSP 502 to decodeglobal positioning system signals, thereby enabling the UE 110 todetermine its position. Various other peripherals may also be includedto provide additional functions, e.g., radio and television reception.

FIG. 6 illustrates a software environment 602 that may be implemented bythe DSP 502. The DSP 502 executes operating system drivers 604 thatprovide a platform from which the rest of the software operates. Theoperating system drivers 604 provide drivers for the node hardware withstandardized interfaces that are accessible to application software. Theoperating system drivers 604 include application management services(“AMS”) 606 that transfer control between applications running on the UE110. Also shown in FIG. 6 are a web browser application 608, a mediaplayer application 610, and Java applets 612. The web browserapplication 608 configures the UE 110 to operate as a web browser,allowing a user to enter information into forms and select links toretrieve and view web pages. The media player application 610 configuresthe UE 110 to retrieve and play audio or audiovisual media. The Javaapplets 612 configure the UE 110 to provide games, utilities, and otherfunctionality. A component 614 might provide functionality describedherein.

The UE 110 and other components described above might include aprocessing component that is capable of executing instructions relatedto the actions described above. FIG. 7 illustrates an example of asystem 1300 that includes a processing component 1310 suitable forimplementing one or more embodiments disclosed herein. In addition tothe processor 1310 (which may be referred to as a central processor unitor CPU), the system 1300 might include network connectivity devices1320, random access memory (RAM) 1330, read only memory (ROM) 1340,secondary storage 1350, and input/output (I/O) devices 1360. In somecases, some of these components may not be present or may be combined invarious combinations with one another or with other components notshown. These components might be located in a single physical entity orin more than one physical entity. Any actions described herein as beingtaken by the processor 1310 might be taken by the processor 1310 aloneor by the processor 1310 in conjunction with one or more componentsshown or not shown in the drawing.

The processor 1310 executes instructions, codes, computer programs, orscripts that it might access from the network connectivity devices 1320,RAM 1330, ROM 1340, or secondary storage 1350 (which might includevarious disk-based systems such as hard disk, floppy disk, or opticaldisk). While only one processor 1310 is shown, multiple processors maybe present. Thus, while instructions may be discussed as being executedby a processor, the instructions may be executed simultaneously,serially, or otherwise by one or multiple processors. The processor 1310may be implemented as one or more CPU chips.

The network connectivity devices 1320 may take the form of modems, modembanks, Ethernet devices, universal serial bus (USB) interface devices,serial interfaces, token ring devices, fiber distributed data interface(FDDI) devices, wireless local area network (WLAN) devices, radiotransceiver devices such as code division multiple access (CDMA) and/orglobal system for mobile communications (GSM) radio transceiver devices,and other well-known devices for connecting to networks. These networkconnectivity devices 1320 may enable the processor 1310 to communicatewith the Internet or one or more telecommunications networks or othernetworks from which the processor 1310 might receive information or towhich the processor 1310 might output information.

The network connectivity devices 1320 might also include one or moretransceiver components 1325 capable of transmitting and/or receivingdata wirelessly in the form of electromagnetic waves, such as radiofrequency signals or microwave frequency signals. Alternatively, thedata may propagate in or on the surface of electrical conductors, incoaxial cables, in waveguides, in optical media such as optical fiber,or in other media. The transceiver component 1325 might include separatereceiving and transmitting units or a single transceiver. Informationtransmitted or received by the transceiver 1325 may include data thathas been processed by the processor 1310 or instructions that are to beexecuted by processor 1310. Such information may be received from andoutputted to a network in the form, for example, of a computer databaseband signal or signal embodied in a carrier wave. The data may beordered according to different sequences as may be desirable for eitherprocessing or generating the data or transmitting or receiving the data.The baseband signal, the signal embedded in the carrier wave, or othertypes of signals currently used or hereafter developed may be referredto as the transmission medium and may be generated according to severalmethods well known to one skilled in the art.

The RAM 1330 might be used to store volatile data and perhaps to storeinstructions that are executed by the processor 1310. The ROM 1340 is anon-volatile memory device that typically has a smaller memory capacitythan the memory capacity of the secondary storage 1350. ROM 1340 mightbe used to store instructions and perhaps data that are read duringexecution of the instructions. Access to both RAM 1330 and ROM 1340 istypically faster than to secondary storage 1350. The secondary storage1350 is typically comprised of one or more disk drives or tape drivesand might be used for non-volatile storage of data or as an over-flowdata storage device if RAM 1330 is not large enough to hold all workingdata. Secondary storage 1350 may be used to store programs that areloaded into RAM 1330 when such programs are selected for execution.

The I/O devices 1360 may include liquid crystal displays (LCDs), touchscreen displays, keyboards, keypads, switches, dials, mice, track balls,voice recognizers, card readers, paper tape readers, printers, videomonitors, or other well-known input devices. Also, the transceiver 1325might be considered to be a component of the I/O devices 1360 instead ofor in addition to being a component of the network connectivity devices1320. Some or all of the I/O devices 1360 may be substantially similarto various components depicted in the previously described drawing ofthe UE 110, such as the display 402 and the input 404.

In an embodiment, a method for a network component to handle requestssent to the network component is provided. The network componentinspects requests sent to the network component to determine if therequests are related to emergencies, and if one of the requests isdetermined to relate to an emergency, the network component updates therequest.

When the request is determined to relate to an emergency, the networkcomponent is alternatively configured, based on configurations andregulator policies, to perform one of: accepting the request; acceptingthe request and including an emergency call indicator in a SessionInitiation Protocol (SIP) response sent to a user equipment (UE) thatinitiated the request; not accepting the request by rejecting therequest; not accepting the request and indicating alternative contactinformation for an emergency response center to which the request wasdirected.

In an embodiment, a SIP (Session Initiated Protocol) response is sent tothe UE in response to the UE making a call that the UE is unaware is anemergency call.

If a globally routable user agent uniform resource identifier (GRUU) isassociated with the UE, and if the GRUU is a temporary GRUU, thetemporary GRUU is replaced with a non-temporary GRUU. The temporary GRUUmight be replaced with the non-temporary GRUU only when a request is notmade to keep the GRUU private.

If an IMS Communication Service Identifier (ICSI) or an IMS ApplicationReference Identifier (IARI) is present, before the Request is routed toa PSAP or emergency centre, the network component performs at least oneof: removing P-Preferred-Service header fields; removingP-Asserted-Service header fields; removing ICSI feature tags and tagvalues from the Accept-Contact header fields; and removing IARI featuretags and tag values from the Accept-Contact header fields.

When the network component does not accept the request, the networkcomponent responds with one of a 300 (Multiple Choices) message, a 301(Moved Permanently) message, a 302 (Moved Temporarily) message, a SIP4xx response, a SIP 6xx response, a SIP 380 (Alternative Service)response.

In an embodiment, the network component does not accept the request dueto at least one of: the network not being able to handle emergencysessions; an internet multimedia core network subsystem to which thenetwork component belongs not being able to handle emergency sessions;the network not handling emergency sessions due to local policy; thenetwork only handling certain types of emergency session requests; theUE roaming; the network component being in a different network than theUE's home operator's network; and the network not supporting emergencysessions for one of the geographical location where the UE is locatedand the Internet Protocol Connectivity Access Network to which the UE isattached.

In an embodiment, the network component includes a configurable listwith local and roaming partners' emergency service identifiers thatindicate on a per emergency service identifier basis the handling ofrequests. When the network component does not accept the request, aconfigurable list of alternate emergency service identifiers is sent tothe UE. The at least one alternative emergency service URI might bepresented to the user of the UE.

In an embodiment, the network component, rather than not accepting therequest for an unsupported emergency service type, prepares the requestfor forwarding to the UE's home network. The UE's home network might beconfigured to handle the URI value associated with the request.

In an embodiment, the network component is a proxy call session controlfunction (P-CSCF).

In an embodiment, the requests comprise initial SIP requests for adialog, standalone SIP transactions, unknown SIP methods.

In an alternative embodiment, a user equipment is provided. The userequipment comprises a component, such that responsive to making anemergency request that is rejected, the component is configured toreceive a message containing information associating the emergencyrequest with a combined emergency centre. The component may be furtherconfigured to use the information to make a subsequent emergency requestto the combined emergency centre.

In an alternative embodiment, a network component is provided. Thenetwork component comprises a component, such that upon receiving anemergency request from a user equipment, the component is configured todetermine whether the emergency request is related to a combinedemergency centre and to send the user equipment a message containinginformation identifying that the emergency request is related to acombined emergency centre.

In an alternative embodiment, a user equipment is provided. The userequipment comprises a component configured to receive a reject messagecontaining alternate address information associating an emergencyrequest with a plurality of emergency centres, non-emergency centres, orcombined emergency centres. The alternate address information can beused to determine to which one of the plurality of centres an emergencycall should be routed.

In an alternative embodiment, a network component is provided. Thenetwork component comprises a component configured to determine whethera received request is an emergency request and whether the receivedrequest is related to one or more specific emergency centres, combinedemergency centres, or non-emergency centres and to send a rejectionresponse containing alternate address information. The alternate addressinformation can comprise a mapping between the received request, a phonecontext and one or more optional emergency identifier types.

The following 3rd Generation Partnership Project (3GPP) TechnicalSpecifications (TS) are incorporated herein by reference: TS 24.229V7.8.0 (2007 December) and TS 24.008.

While several embodiments have been provided in the present disclosure,it should be understood that the disclosed systems and methods may beembodied in many other specific forms without departing from the spiritor scope of the present disclosure. The present examples are to beconsidered as illustrative and not restrictive, and the intention is notto be limited to the details given herein. For example, the variouselements or components may be combined or integrated in another systemor certain features may be omitted, or not implemented.

Also, techniques, systems, subsystems and methods described andillustrated in the various embodiments as discrete or separate may becombined or integrated with other systems, modules, techniques, ormethods without departing from the scope of the present disclosure.Other items shown or discussed as coupled or directly coupled orcommunicating with each other may be indirectly coupled or communicatingthrough some interface, device, or intermediate component, whetherelectrically, mechanically, or otherwise. Other examples of changes,substitutions, and alterations are ascertainable by one skilled in theart and could be made without departing from the spirit and scopedisclosed herein.

What is claimed is:
 1. A method for responding to an emergency-relatedmessage by a network node, the network node within a trust domain, themethod comprising: receiving, from a user equipment (UE), a firstSession Initiation Protocol (SIP) request message; determining, at thenetwork node, that the first SIP request message is an emergency-relatedrequest; based on the determining, including, by the network node, thefollowing in a SIP rejection response message: a P-Asserted-Identityheader field identifying the network node, an indicator indicating thatthe first SIP request message is an emergency-related request, and aContact header field comprising a Uniform Resource Name (URN) of anemergency service; and sending, by the network node, the SIP rejectionresponse message.
 2. The method according to claim 1, wherein the URN ofthe emergency service comprises a code identifying a country.
 3. Themethod according to claim 1, wherein the URN of the emergency servicecomprises a code identifying a region.
 4. The method according to claim1, further comprising: receiving a second SIP request message, whereinthe second SIP request message comprises the URN of the emergencyservice, and emergency-related information associated with the UE. 5.The method according to claim 4, further comprising: sending a messagebased on the second SIP request message towards a Public SafetyAnswering Point (PSAP).
 6. The method of claim 4, wherein theemergency-related information associated with the UE included in thesecond SIP request message comprises at least one of a UE location or UEaccess network information.
 7. The method according to claim 1, wherein,prior to sending the SIP rejection response message, the UE is unawarethat the first SIP request message is an emergency-related request. 8.The method according to claim 1, wherein the network node comprises aproxy call session control function (P-CSCF).
 9. A network node within atrust domain, the network node comprising: at least one hardwareprocessor; and a non-transitory computer-readable storage medium coupledto the at least one hardware processor and storing programminginstructions for execution by the at least one hardware processor,wherein the programming instructions, when executed, cause the networknode to perform operations comprising: receiving, from a user equipment(UE), a first Session Initiation Protocol (SIP) request message;determining, at the network node, that the first SIP request message isan emergency-related request; based on the determining, including, bythe network node, the following in a SIP rejection response message: aP-Asserted-Identity header field identifying the network node, anindicator indicating that the first SIP request message is anemergency-related request, and a Contact header field comprising aUniform Resource Name (URN) of an emergency service; and sending, by thenetwork node, the SIP rejection response message.
 10. The network nodeaccording to claim 9, wherein the URN of the emergency service comprisesa code identifying a country.
 11. The network node according to claim 9,wherein the URN of the emergency service comprises a code identifying aregion.
 12. The network node according to claim 9, the operationsfurther comprising: receiving a second SIP request message, wherein thesecond SIP request message comprises the URN of the emergency service,and emergency-related information associated with the UE.
 13. Thenetwork node according to claim 12, the operations further comprising:sending a message based on the second SIP request message towards aPublic Safety Answering Point (PSAP).
 14. The network node according toclaim 12, wherein the emergency-related information associated with theUE included in the second SIP request message comprises at least one ofa UE location or UE access network information.
 15. The network nodeaccording to claim 9, wherein, prior to sending the SIP rejectionresponse message, the UE is unaware that the first SIP request messageis an emergency-related request.
 16. The network node according to claim9, wherein the network node comprises a proxy call session controlfunction (P-CSCF).
 17. A non-transitory computer-readable medium storinginstructions which, when executed, cause a computing device to performoperations comprising: receiving, from a user equipment (UE), a firstSession Initiation Protocol (SIP) request message; determining, at anetwork node within a trust domain, that the first SIP request messageis an emergency-related request; based on the determining, including, bythe network node, the following in a SIP rejection response message: aP-Asserted-Identity header field identifying the network node, anindicator indicating that the first SIP request message is anemergency-related request, and a Contact header field comprising aUniform Resource Name (URN) of an emergency service; and sending, by thenetwork node, the SIP rejection response message.
 18. The non-transitorycomputer-readable medium according to claim 17, wherein the URN of theemergency service comprises a code identifying a country.
 19. Thenon-transitory computer-readable medium according to claim 17, whereinthe URN of the emergency service comprises a code identifying a region.20. The non-transitory computer-readable medium according to claim 17,wherein the network node comprises a proxy call session control function(P-CSCF).